The present study aimed to examine the effects of the Quality Book Reading (NIKO) Early Intervention Program on Turkish mothers of children with Down syndrome aged between 2 and 6 years and their children. The research was conducted using the convergent parallel mixed design with 17 mother-child dyads determined by random assignment. Nine participants were included in the control group, and eight were included in the intervention group. The research was performed online. The research data were collected through video recordings of the mother-child dyads taken during the book reading activity before and after the intervention and semi-structured interviews conducted with the mothers after the intervention. Results revealed that the NIKO Program was effective on various variables, which are primarily children's pivotal behaviours, interactional behaviours, and book reading behaviours displayed by mothers. Parents exhibited more quality reading behaviours and these behaviours positively impacted the pivotal behaviours and interactions of children. The above-mentioned results show that the NIKO Program can contribute to the development of children with Down syndrome and is an effective tool for parents to improve their book reading habits.